A variety of GABAA receptor subunit-specific antibodies have been generated and have been used for purifying GABAA receptor subtypes from brain membrane extracts by immunoprecipitation or immunoaffinity chromatography. These studies indicated an extreme promiscuity of the various subunits. Although the antibodies used were highly specific for the respective subunits, most if not all of the other subunits investigated could be co-purified with antibodies directed against an individual α or β subunit, suggesting that α and β subunits can combine with most of the other subunits to form a variety of different receptor subtypes. These studies also indicate that two different α and two different β subunits can be present in GABAA receptors. In contrast, most studies agreed that γ subunits could not be co-precipitated with other γ subunits. Similarly, δ subunits seem not to be present together with γ subunits in the same receptors (for review see Sieghart and Sperk, 2002). From these results a subunit stoichiometry of 2α, 2β and 1γ or 1δ subunit can be deduced for native receptors. This conclusion was confirmed in several recombinant receptor studies,
